The metal-semiconductor-metal (MSM) structure ultraviolet (UV) photodetector p assivated by SiO_2passivation layer (with SiO₂SPL) was fabricated on the nonpolar AlGaN grown by metalorganic chemical vapor deposition (MOCVD).The results indicate that th e surface passivation of SiO₂SPL is an important way to enhance the UV performance of t he nonpolar AlGaN-MSM UV photodetector.The fabricated devices are characterized by measurin g the dark current characteristic and the spectral response.It is found that the dark current of the UV photodetector is decreased by 2-3orders of magnitude after being passivated by SiO₂SPL.When the reverse voltage is 5V,the UV photodetector exhibits a sh arp cut-off wavelength at about 300nm,the spectral response is increased by 10^3times,and the rejection ratio of photode tector as high as 10⁵.